Many inner city play areas are smaller than regulation size baseball or softball fields and frequently are partially or fully paved with blacktop or concrete. Regulation game balls not only can outdistance the size of such playing fields, but also do not possess the durability to withstand the harsh surface condition of these paved areas.
Reduced injury factor or "safety" balls have been used in limited playing field areas as well as for indoor and outdoor training, and for competitive use by young players. Such balls exhibit severely limited flight characteristics and/or do not have the requisite durability for harsh surface conditions. They typically have a core which is formed of a foamed polymer (U.S. Pat. No. 4,772,019) or a soft cloth (U.S. Pat. No. 4,261,565) and a cover which is made of cloth. U.S. Pat. No. 4,772,019 discloses a safety ball with a cold cure polyester-polyether based urethane core and a nylon cover stitched with chain or herringbone stitching. The cover is permitted to move or be resiliently displaced relative to the core to control the rebound characteristics of the ball. U.S. Pat. No. 5,253,865 also is directed to a safety ball with a foam urethane core and a flexible cloth cover. Other known "softer" game balls have a kapok core covered with a synthetic or natural stitched leather cover or may have a hollow spherical core as disclosed in U.S. Pat. Nos. 4,880,233 and 5,123,659.
The advantage of reduced injury factor balls is that they have a reduced impact pressure, and therefore are less apt to "sting" upon hitting a player. Furthermore, they are less likely to cause damage if they are hit or thrown against an object or structure. However, conventional safety balls also often have poor durability, including the tendency to severely deform from their original spherical shape. Furthermore, the covers of stitched safety balls tend to separate from their cores. Therefore, conventional safety balls are not well suited for long-term use or for use on hard surfaces such as concrete or pavement often found in inner city play areas.